This invention relates to a method for manufacturing a chemically adsorbed film on the surface of a substrate comprising active hydrogens via siloxane bonding and a chemically adsorbent solution for using therefor. More particularly, this invention relates to a method for manufacturing a chemically adsorbed film using an alkoxysilane surface active agent, a nonaqueous solvent and a silanol condensing catalyst and a chemical adsorbent solution using therefor.
The surface of the substrate such as plastic, metal, ceramics, fiber, woods, concrete, paint or the like have been treated for improved use in a variety of fields. For example, a method for treating a surface containing macromolecules includes; coating with a fluorosilane coupling agent to provide water and oil repellency; coating with a wax to provide lubrication; coating with a polyvinyl alcohol to provide hydrophilicity; and coating with a suspension of a fluorocarbon-based polymer in order not to catch dirt on the surface of a substrate. The above-mentioned methods are recognized in the field.
However, coating films of the prior art have a relatively weak binding strength to the substrates containing macromolecules. Consequently, if the substrates are wiped by a cloth or washed repeatedly, coating films are peeled off from the substrate and lose the finishing effect. Moreover, coating films of the prior art have a large number of pin-holes on their surfaces because molecules arrange in various directions therein, thus deteriorating the property. Moreover, fluorocarbon-based polymer coating films are deficient in transparency so that they cannot be used for the treatment of optical materials that require transparency.
Methods for manufacturing chemically adsorbed monomolecular films are suggested by the inventor of this invention. See, for example, Japanese Laid-Open Patent No.(Tokkai-Hei) 4-132637, Japanese Laid-Open Patent No.(Tokkai-Hei) 4-221636, Japanese Laid-Open Patent No.(Tokkai-Hei) 4-367721 which are incorporated by reference. Such films are free from peeling off from the substrates, being pin-hole free, having thickness on the order of nanometers, and having a high transparency, in other words, transparency and lustering properties.
However, according to the conventional method for manufacturing chemically adsorbed films, the films were formed by a dehydrochloric reaction between a chlorosilane-based surface active agent and the surface of a substrate. Consequently, harmful hydrochloric acid gas can generate during the formation of such films. Also certain methods have attempted to form films by a dealcohol reaction by way of an alkoxysilane surface active agents. However, since this reaction proceeds slowly, films are not easily formed. The method of using a dealcohol catalyst is also possible, but the surface active agent cross-links with the moisture content in the air and loses the activity if only the dealcohol catalyst is added. In other words, if the finishing agent includes moisture, the surface active agent cross-links before reacting to the surface of the substrate so that the reaction at the interface of solid and liquid is prevented, thus making chemically adsorption difficult.
To solve the above-noted problems, the invention aims to provide a method of forming a chemically adsorbed film which allows practical reaction rates and does not generate hydrochloric acid gas in forming the films.
To attain the above aim, the invention provides a first method of forming a chemically adsorbed film on a substrate having an active hydrogen, comprising the step of contacting the substrate with a solution mixture containing an alkoxysilane surface active agent, an active hydrogen-free nonaqueous solvent and silanol condensing catalyst to form a chemically adsorbed film covalently bonded to a surface of the substrate via siloxane bonding. The term xe2x80x9cactive hydrogen-free nonaqueous solventxe2x80x9d relates to a nonaqueous solvent containing substantially no active hydrogen. Preferably, it is free of all active hydrogen. The nonaqueous solvents can include any solvents other than water.
The first method can comprise contacting the substrate with the solution mixture containing the alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the alkoxysilane surface active agent to the surface of the substrate via a siloxane bond, and washing the substrate with a nonaqueous solvent to form a monomolecular coating film covalently bonded to the surface of the substrate via a siloxane bond. This method efficiently forms a monomolecular film made from the surface active agent, and the film is covalently bonded to the surface of the substrate via siloxane bonds.
The first method can also comprise contacting the substrate with a solution mixture containing the alkoxysilane surface active agent, the active hydrogen-free non aqueous solvent and the silanol condensing catalyst, covalently bonding the alkoxysilane surface active agent to the surface of the substrate via siloxane bonds, evaporating the nonaqueous solvent, and subjecting the substrate and the alkoxysilane surface active agent to a reaction with water to form a coating of a polymer film covalently bonded to the surface of the substrate via siloxane bonds. This method efficiently forms a polymer coating film made from the surface active agent, and the film is covalently bonded to the surface of the substrate via siloxane bonds.
The invention further provides a second method comprising the steps of contacting the substrate with a solution mixture containing a first alkoxysilane surface active agent, an active hydrogen-free nonaqueous solvent and a silanol condensing catalyst to form an inner layer which is a siloxane chemically adsorbed film covalently bonded to a surface of the substrate via a siloxane bond, and contacting the inner layer with a solution mixture containing at least a second alkoxysilane surface active agent, an active hydrogen-free nonaqueous solvent and a silanol condensing catalyst to form an outer layer made from a second alkoxysilane surface active agent and covalently bonded to a surface of the inner layer via a siloxane bond. In this embodiment, the first alkoxysilane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetraalkoxysilane. This method efficiently forms a bi-layer chemically adsorbed film having an inner layer which is a chemically adsorbed monomolecular film of siloxane and an outer layer which is a chemically adsorbed monomolecular film from the second alkoxysilane surface active agent.
The second method can comprise contacting the substrate with the solution mixture containing the first alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the first alkoxysilane surface active agent to the surface of the substrate via a siloxane bond, washing the substrate with a nonaqueous solvent to form the inner layer which comprises a siloxane and is a chemically adsorbed monomolecular film covalently bonded to a surface of the substrate via a siloxane bond and then contacting the substrate covered with the inner layer with a solution mixture containing the second alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the second alkoxysilane surface active agent to the surface of the inner layer via a siloxane bond, and washing the substrate with a nonaqueous solvent to form an outer layer made from the second alkoxysilane surface active agent and covalently bonded to a surface of the inner layer via a siloxane bond. The first alkoxysilane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetraalkoxysilane. This method efficiently forms a chemically adsorbed bi-layer film having an inner layer which is a chemically adsorbed monomolecular film made from siloxane and an outer layer which is a chemically adsorbed monomolecular film made from a second alkoxysilane surface active agent.
The second method can also comprise contacting the substrate with a solution mixture containing the first alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the first alkoxysilane surface active agent to the surface of the substrate via a siloxane bond, washing the substrate with a nonaqueous solvent to form a siloxane inner layer and covalently bonded to a surface of the substrate via a siloxane bond and then, contacting the substrate with a solution mixture containing at least the second alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the second alkoxysilane surface active agent to the surface of the inner layer via a siloxane bond, evaporating the nonaqueous solvent on the substrate, and subjecting an alkoxy group in the second alkoxsilane surface active agent remaining on the surface of the inner layer to a reaction with water to form an outer layer made from the second alkoxysilane surface active agent and covalently bonded to a surface of the inner layer via a siloxane bond. The first alkoxysilane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetralkoxysilane. This method efficiently forms a bi-layer chemically adsorbed film having an inner layer which is a chemically adsorbed monomolecular film of siloxane and an outer layer which is a chemically adsorbed polymer film from the second alkoxysilane surface active agent.
The second method can also comprise contacting the substrate with a solution mixture containing the first alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the first alkoxysilane surface active agent to the surface of the substrate via a siloxane bond, evaporating the nonaqueous solvent on the substrate, subjecting an alkoxy group in the second alkoxysilane surface active agent remaining on the surface of the substrate to a reaction with water to form an inner layer which comprises a polysiloxane and is a film covalently bonded to a surface of the inner layer via a siloxane bond, contacting the substrate with the solution mixture containing at least the second alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the second alkoxysilane surface active agent to the surface of the inner layer via a siloxane bond, and washing the substrate and the second alkoxysilane surface active agent with a nonaqueous solvent to form the outer layer made from the second alkoxysilane surface active agent and covalently bonded to the surface of the substrate via a siloxane bond. The first alkoxysilane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetralkoxysilane. This method efficiently forms a bi-layer chemically adsorbed film having an inner layer which comprises polysiloxane and an outer layer which is a chemically adsorbed monomolecular film from the second alkoxysilane surface active agent.
The second method can also comprise contacting the substrate with a solution mixture containing the first alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the first alkoxysilane surface active agent to the surface of the substrate via a siloxane bond, evaporating the nonaqueous solvent, subjecting an alkoxy group in the first alkoxysilane surface active agent remaining on the surface of the substrate to a reaction with water to form the inner layer which comprises polysiloxane and is a film covalently bonded to the surface of the substrate via a siloxane bond, contacting the substrate with the solution mixture containing at least the second alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the second alkoxysilane surface active agent to the surface of the inner layer via a siloxane bond, evaporating the nonaqueous solvent on the substrate, and subjecting an alkoxy group in the second alkoxysilane surface active agent remaining on the surface of the inner layer to a reaction with water to form the outer layer made from the second alkoxysilane surface active agent and covalently bonded to the surface of the inner layer. The first alkoxysilane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetralkoxysilane. This method efficiently forms a bi-layer chemically adsorbed film having an inner layer which comprises polysiloxane and an outer layer which is a polymer film from the second alkoxysilane surface active agent.
The invention further provides a third method comprising the step of contacting a substrate with a solution mixture containing a silane surface active agent, an active hydrogen-free nonaqueous solvent and a silanol condensing catalyst to form a chemically adsorbed film which comprises a siloxane and is covalently bonded to a surface of the substrate via a siloxane bond. The silane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetralkoxysilane. This method efficiently forms a hydrophilic chemically adsorbed thin film comprising siloxane.
The third method can comprise contacting the substrate with the solution mixture containing the silane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the silane surface active agent to the surface of the substrate via a siloxane bond, and washing the substrate with a nonaqueous solvent to form a chemically adsorbed monomolecular film which comprises a siloxane and is covalently bonded to the surface of the substrate via a siloxane bond. The silane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetralkoxysilane. This method efficiently forms a hydrophilic monomolecular film comprising siloxane.
The third method can also comprise contacting the substrate with the solution mixture containing the silane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the silane surface active agent to the surface of the substrate via a siloxane bond, evaporating the nonaqueous solvent on the substrate, and subjecting an alkoxy group in the silane surface active agent remaining on the surface of the substrate to a reaction with water to form a film which comprises a polysiloxane and is a film covalently bonded to the surface of the substrate via a siloxane bond, and the silane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetralkoxysilane. This method efficiently forms a hydrophilic polymer film comprising siloxane.
The silanol condensing catalyst is preferably at least one substance selected from the group consisting of metal carboxylate, carboxylic acid ester metal salt, metal carboxylate polymer, metal carboxylate chelate, titanic ester and titanic ester chelate. These catalysts have good catalytic activity. Examples of such catalysts include tin (I) acetate, dibutyl tin dilaurate, dibutyl tin dioctate, dibutyl tin diacetate, dioctyl tin dilaurate, dioctyl tin dioctate, dioctyl tin diacetate, tin (I) dioctanate, lead naphthenate, cobalt naphthenate, iron 2-ethyl hexenoic acetate, dioctyl tin bis-octyl thioglycollic acid ester salt, dioctyl tin maleic acid ester salt, dibutyl tin maleic acid polymer, dimethyl tin mercapto propionic acid salt polymer, dibutyl tin bis-acetyl acetonate, dioctyl tin bis-acetyl laurate, tetrabutyl titanate, tetranonyl titanate and bis-(acetylacetonyl) di-propyltitanate. The catalysts can be used either alone or in combination.
The silane surface active agent preferably comprises a fluorocarbon group. Such silane surface active agents comprising a fluorocarbon group provides secondly formed, e.g., outer layers with properties of water, oil and dirt repellancy. Examples of such silane surface active agents include substances represented by one formula selected from the following two formulas:
CF3xe2x80x94(CF2)nxe2x80x94(R)mxe2x80x94SiXp(OA)3-p
wherein n is 0 or an integer, R represents an alkylene group, vinylene group, ethynylene group, arylene group, or a substituent containing a silicon atom or oxygen atom, m is 0 or 1, X represents an hydrogen atom, alkyl group, alkoxy group, fluorine-containing alkyl group or fluorine-containing alkoxy group, A represents an alkyl group, and p is an integer of 0, 1 or 2; and
CF3COOxe2x80x94(CH2)wxe2x80x94SiXp(OA)3-p
wherein w is an integer, X represents an hydrogen atom, alkyl group, alkoxy group. fluorine-containing alkyl group or fluorine-containing alkoxy group, A represents an alkyl group, and p is an integer of 0, 1 or 2.
The substrate preferably comprises at least one material selected from the group consisting of metal, ceramic, glass, plastic, paper, fabric and leather. When formed of, e.g., plastic or synthetic fiber fabric, the substrate preferably has been made hydrophilic by treating the substrate either with a plasma containing oxygen or in a corona atmosphere. The treatment allows molecules of the surface active agents to fix on the substrates in high concentrations.
The nonaqueous solvent is preferably a water-free solvent comprising a hydrocarbon or a water-free solvent comprising a fluorocarbon. Fluorocarbon-based solvents, especially, are easy to use because they are less harmful. The term xe2x80x9cwater-free solventxe2x80x9d relates to a solvent containing substantially no water.
The invention further provides a chemical adsorbent solution comprising a solution mixture containing an alkoxysilane surface active agent, an active hydrogen-free nonaqueous solvent and a silanol condensing catalyst. The chemical adsorbent solution can contain other ingredients as long as the ingredient does not inhibit catalytic reaction.
The silanol condensing catalysts disclosed above are also available for the chemical adsorbent solution of the invention.
The chemical adsorbent solution of the invention can also contain the alkoxysilane surface active agent comprising a fluorocarbon group, specifically substances represented by one formula selected from the above-mentioned two formulas.
The chemical adsorbent solution of the invention can also contain nonaqueous solvents selected from, for example, water-free solvents comprising a hydrocarbon and a water-free solvent comprising a fluorocarbon, and silicone solvents or the mixture.
The chemical adsorbent solution of the invention preferably has a water content of 10 ppm or less. The low water content is helpful for keeping stabilities of alkoxysilane surface active agents and silanol condensing catalysts and for keeping pot life of the chemical adsorbent solution.
It is preferable in the chemical adsorbent solution of the invention that 100 weight parts of the solution mixture comprises 0.1 to 30 weight parts of the alkoxysilane surface active agent, 0.0001 to 7.5 weight parts of the silanol condensing catalyst, and 62.5 to 99.8999 weight parts of the active hydrogen-free nonaqueous solvent.
The invention is capable of providing method for forming a chemically adsorbed film which allows practical reaction rates and does not generate acid gas in forming the films. When the surface of substrates is treated with hexaalkoxydisiloxane, octaalkoxytrisiloxane, dialkoxysilane, trialkoxysilane or tetraalkoxysilane prior to the formation of chemically adsorbed films, high density of silanol bonds can be provided on the surface of the substrates. Preferable silanol condensing catalysts are metal carboxylate, carboxylic acid ester metal salt, metal carboxylate polymer, metal carboxylate chelate, titanic ester or titanic ester chelate. Those catalysts can be more useful than acid catalysts in controlling reaction rate. The alkoxysilane surface active agents comprising a fluorocarbon group improves water- and oil-repellent properties of the obtained coating films. In particular, substances represented by the above two formulas allow the formation of chemically adsorbed films with high density. Further, the water-free hydrocarbon-based nonaqueous solvents or the water-free fluorocarbon-based nonaqueous solvents allow the formation of chemically adsorbed films with high density without decreasing catalytic activities of the catalysts. The fluorocarbon-based nonaqueous solvents are particularly useful for forming polymer films because the solvents have a low specific heat and evaporate quickly.
When a substrate such as plastic and synthetic fiber fabric has little active hydrogen atoms on its surface, the substrate is preferably treated either with a plasma containing oxygen or in a corona atmosphere to make the surface hydrophilic. The treatment allows the formation of chemically adsorbed films on the surface of polymers. It was relatively difficult for conventional methods to form chemically adsorbed films on the polymers.
The chemical adsorbent solution of the invention realizes a useful chemical adsorbent solution.